The invention relates generally to marine engines, and more particularly, to propeller hubs.
Outboard engines include a drive shaft which extends from the engine power head, through an exhaust case, and into an engine lower unit. The lower unit includes a gear case, and a propeller shaft extends through the gear case. Forward and reverse gears couple the propeller shaft to the drive shaft. The drive shaft, gears, and propeller shaft sometimes are referred to as a drive train.
A propeller is secured to and rotates with the propeller shaft. Torque from the propeller is transmitted to the shaft. Specifically, propeller hub assemblies transmit torque to the propeller shaft. Exemplary propeller hub assemblies include cross bolts, keys, shear pins, plastic hubs, and compressed rubber hubs. Such hub assemblies should have sufficient strength or stiffness so that during normal engine operations, very few losses occur between the propeller shaft and the propeller. Such hub assemblies, however, also should be resilient so that the engine drive train is protected in the event of an impact, e.g., if the propeller hits a log or rock.
A propeller hub assembly also should facilitate xe2x80x9climp homexe2x80x9d operation of the engine so that even in the event that an interface between the propeller shaft and the propeller shears due to a large impact, the propeller and propeller shaft still remain sufficiently engaged so that the engine still drives the boat, for example, to return to a dock for repairs. Further, since engine manufacturers often utilize different propeller shaft arrangements, it would be desireable to provide propeller hub assemblies that facilitate use of one propeller on engines of different engine manufacturers.
These and other objects may be attained by a propeller assembly that includes an interchangeable drive sleeve, a resilient inner hub having a bore in which the drive sleeve is inserted, and a propeller including an outer hub in which the drive sleeve and resilient inner hub are inserted. In an exemplary embodiment, the drive sleeve includes a cylindrical shaped body and a plurality of splines extend from an outer diameter surface of drive sleeve body. A bore extends through drive sleeve, and a plurality of grooves are in an inner diameter surface of the drive sleeve bore. These grooves are configured to mate with splines on a propeller shaft.
Resilient inner hub includes a cylindrical shaped body and a plurality of tapered grooves in an inner diameter surface of the inner hub body. Each groove is arranged to receive one drive sleeve spline. The inner hub also includes a drive flange at one end thereof.
The propeller includes an outer hub having a cylindrical shaped body, and a plurality of blades extend from an outer diameter surface of the outer hub body. An inner diameter surface of the outer hub body is shaped to mate with the inner hub drive flange to limit relative movement between the inner hub drive flange and the outer hub.
For limp home operation, the drive sleeve includes a flange at one end of the drive sleeve cylindrical shaped body, and a plurality of limp home projections, or drive arms, extend from the drive sleeve flange. A plurality of limp home projections, or drive arms, also extend from the outer hub inner diameter surface.
During operation, and upon the occurrence of an impact, resilient hub twists along its axial length, and drive sleeve splines progressively come into contact with side walls of grooves in inner hub. When the splines are in contact with one groove side wall along the entire length of wall, such contact limits further twisting by inner hub. The operational condition in which hub is twisted along its axial length as described above is sometimes referred to herein as the resilient operation mode.
If the impact forces are sufficient, it is possible that the splines will shear. In the event that all splines shear, then the propeller shaft and drive sleeve rotate relative to the propeller outer hub until the limp home arm projections of the drive sleeve and outer hub come into contact. If the forces are not sufficient to also shear the limp home projections, then the propeller will resume rotating with the propeller shaft. Such operational condition is sometimes referred to herein as the limp home operation mode.
In addition to operating in both a resilient mode to protect the engine drive train from damage, and a limp home mode so that even in the event that the propeller strikes an object in the water, the propeller is still operational, the above described propeller assembly facilitates the easy replacement of the resilient hub. Specifically, in the event that the inner hub needs to be replaced, a user simply removes the propeller assembly from the propeller shaft, and removes the drive sleeve and resilient hub from within the outer hub. A replacement inner hub can then be utilized when reassembling the propeller assembly and mounting the assembly on the propeller shaft.
Further, different drive sleeves can be provided so that the propeller can be utilized on many different types of marine engines. For example, one particular marine engine may have splines on the propeller shaft of a first length, and another particular marine engine may have splines on a propeller shaft of a second length. Different drive sleeves having different length splines on their inner diameter surfaces can be provided. Although different drive sleeves a reutilized, a same propeller can be used. That is, by providing inter changeable drive sleeves, one propeller can be used in conjunction with many different type engines.